The main switch and the forward/reverse switch are conveniently combined in a single integrated switch unit. Such integrated switch units generally includes a first actuator which is actuated via a trigger switch, which trigger switch is depressed by a user to turn the motor on and released to turn the motor off. Generally the speed of the motor can also be controlled depending on the extent that the trigger switch and thus the first actuator is depressed. An electronic control unit, is generally incorporated within the integrated switch unit, and is responsive to the first actuator to apply the appropriate current to the motor. The integrated switch unit will also generally include a second actuator which can be moved between two positions via a forward/reverse lever moveable by a user. The electronic control unit is also generally responsive to the second actuator and in a first forward position of the second actuator the electronic control unit will drive the motor in a forward direction of rotation and in a second reverse position of the second actuator the electronic control unit will drive the motor in a second reverse direction.
In order to prevent damage to the tool, the main switch and the forward/reverse switch are generally mechanically coupled, so that the position of the forward/reverse switch can only be changed to alter the direction of rotation when the main switch is released, ie. when the motor is switched off.
This mechanical and electronic integration of the main switch and the forward/reverse switch suffers from the disadvantage, that the forward/reverse lever, which is actuated by a user is generally located in the region of the trigger switch of the tool, and so is difficult for a user to see while the tool is being operated. Actuation of the main switch with the forward/reverse switch located in the wrong position may lead to damage to the tool, to a bit driven by the tool or to a fastener to be fixed or released by the tool.
This problem has been addressed in DE33 11 421 by separating the main switch and the forward/reverse switch, so that the forward/reverse switch can be located on an upper surface of the tool which upper surface can generally be seen by a user of the tool in normal operating positions of the tool. This is a disadvantage from a cost and an assembly perspective as two separate switch units are required, as opposed to the preferred type of integrated single switch unit described above. A mechanical interface, in the form of a slideable locking bar, is moved into the path of the trigger switch of the main switch by movement of the forward/reverse switch between the forward and reverse position or vice versa. The mechanical interface is arranged so that when the trigger switch is depressed the trigger switch blocks movement of the locking bar and so prevents movement of the forward/reverse switch between its two positions.